There is a demand for bio-sourced materials as a more environmentally friendly means to construct products. Isosorbides are derived from biologically based sources, namely sugars, rather than from the petroleum feed stocks used to prepare other polymer structural units. Isosorbide-based materials and products have a low net environmental impact, and can be utilized as renewable resources by the plastic manufacturing industry. These materials and products can be used for the production of polymeric materials such as polycarbonates. Polycarbonates are used in hundreds of applications such as eyeglass lenses and optical media, where their transparency and tough physical properties are beneficial.
Light induced degradation is a general problem for all polycarbonate polymers both non-isosorbide base and isosorbide base polymers. The originally ductile polycarbonate becomes brittle due to accelerated chain scission of the polycarbonate due to UV radiation. The degradation of these polymers occurs at the surface of the material. Light stabilizers may be used, but limited choices are available in order to avoid negatively influencing processability (i.e., decrease melt viscosity by molecular weight degradation), and long term thermal aging. HALS in polymers have been used as UV stabilizers as well in polyolefins (polyethylene, polypropylene). Some of them have been marketed as flame retardants as well for these polymers. The only previous HALS used in polycarbonates were piperazinone based HALS for the purpose of acting as a flame retardant and do not provide sufficient UV protection. In non-isosorbide-based polycarbonates, use of sterically hindered amines (HALS) is excluded as HALS dramatically accelerate hydrolysis of polycarbonates.
Accordingly, there is a clear need to provide polymeric compositions that are suitably protected from UV-induced discoloration and degradation.